1. Field of the Invention
The present invention relates to an automatic tape tracking system for magnetic recorder/players and, more particularly, to an automatic system for tracking the lateral position of magnetic tape and adjusting such lateral position to maintain the tape along a predetermined track.
2. Description of the Prior Art
There is always a need for magnetic recorders which can store greater quantities of data at ever increasing data rates. To accomplish this, it is necessary to use wider tape, faster tape speeds and a higher data density (more bits of data per inch of tape). As tape becomes wider and wider, a limiting factor has been the difficulty in guiding the path of the tape through the tape handling system and across the magnetic record/reproduce heads.
By way of example, in developing a magnetic tape handling system for use in an outer space environment, it is presently being proposed to have track widths on the order of 2 mils with a similar spacing between each track. This provides the potential of 600-800 individual tracks across the width of one inch tape. Systems are presently available for use in ground stations for recording 300 megabits of data per second. It can be well appreciated that in handling data having such a density, it is necessary to accurately guide the path of the tape across the heads if the heads are going to remain accurately aligned with the individual data tracks.
Historically, the typical means of guiding tape is either through the use of crown rollers or a fixed edge guidance systems. In the latter approach, flanges forcibly constrain the tape. The problem is that forcibly constraining the tape limits the life thereof. That is, the edges of the tape deteriorate over time and the tape must be replaced. While this does not necessarily present a problem in a ground station, it certainly presents a problem where a system is designed for space application where it will operate over many years without maintenance.
Using crown rollers eliminates the edge flanges, but replaces then with a technique whereby non-uniform stresses are induced across the face of the tape. As tape widths increase, the non-uniform stress must also increase to effect the proper tape tracking performance. The long term presence of non-uniform stresses in the tape results in permanent deformation of the tape. This deformation can alter track-to-track spacing, further complicating the problem of tracking and leading to increased data errors. In addition, the tape deformation limits tape life.